Carious lesion staining solutions, referred to herein as dental Caries Status Disclosing Solutions (CSDS) are presently used in dentistry to indicate caries status.
CSDS stems from early clinical use of water-based silver fluoride followed by stannous fluoride, wherein it was an empirical observation that treated carious lesions that remained black had not progressed (Craig et al., 1981). To investigate this aspect further a clinical trial was conducted to determine whether this phenomenon was, in effect, a reliable indicator of lesion progression. The results indicated that it was (Craig et al., 2013). As such, the combination of silver fluoride followed by stannous fluoride became the basis for CSDS.
CSDS is applied to active carious lesions in primary molars in children, root surface caries, prophylactically, on recurrent caries around restorations and crown and bridgework in the elderly.
The water-based silver fluoride is applied first and, one to three minutes later, the stannous fluoride is placed and acts as a reducing agent for the silver.
The procedure stains an active carious lesion black. If the lesion remains black over a period of time it is an indication that the caries is not progressing (i.e. caries is arrested).
However, if the lesion starts to lighten it is an indication that the caries is progressing.
As such, CSDS is a visual indicator of the status of a carious lesion; namely if it has been arrested or still progressing.
The CSDS may comprise 40% (w/v) silver fluoride and 10% (w/v) stannous fluoride.
Both silver fluoride and stannous fluoride have separately been used as topical agents for various purposes in dentistry for several decades.
For example, an ammoniated version of silver fluoride (38% silver diammine fluoride) was first used in Japan to treat carious lesions in primary teeth (Nishino et al., 1969). Stannous fluoride, at a concentration of 8-10%, was first used in the US as a topical fluoride agent to prevent dental caries. (Howell et al., 1955).
Furthermore, a water-based version of silver fluoride was first used in Australia in the later 1970s in a clinical treatment program for anxious children in Bourke NSW (Craig et al., 1981). The silver fluoride and stannous fluoride used in the study were manufactured and marketed by Creighton Pharmaceuticals of Double Bay NSW and were sold from 1978 to 2002.
Now, a problem exists with the use of silver fluoride in that the silver ion levels in silver fluoride is reduced over time by the adsorption of silver to the container walls. Silver ions have the tendency to “clump” once reduced to metallic silver and so the depletion of silver ions from solution can be marked.
For example, a laboratory evaluation conducted by Dr GG Craig found a water-based 40% (w/v) silver fluoride solution showed a 30% reduction in silver ion levels after aging at 55° C. for 30 days. This testing process is known as aged testing where the temperature is raised above ambient such that 55° C. for 30 days is in fact equivalent to 9 months at ambient temperature of 23° C.
In terms of silver diammine fluoride, ammonia has been used as a stabilising agent to prevent the precipitation of metallic silver from solution. The use of ammonia forms the silver complex Ag(NH3)2+.
Presently, all manufacturers producing silver fluoride dental solution known to the Inventor utilise ammonia for the stabilisation of the solution:
ProductManufacturerStabiliserSaforideToyo Seiyaku Kasei, JapanAmmoniaRiva StarSDI, Bayswater, VictoriaAmmoniaAdvantage ArrestElevate Oral Care, WestAmmoniaPalm Beach, FloridaCariestop (NotBiodinamica, BrazilUses silver nitrate,straight silverboron fluoride influoride useshydrofluoric acid,a complicatedammonia hydroxide andformula towater.produce silverand fluorideions).
However, the use of ammonia as a stabilising agent has disadvantages in terms of smell and the potential for a transitory gingival burn. Although the burn is normally gone after 24 hours it is recommended that the gingival contact by the solution be minimised or avoided completely.
Specifically, according to Horst et al., 2016, in 9 randomized clinical trials involving children or elders monitored for 1-3 years in which silver diammine fluoride was applied to multiple teeth to arrest or prevent dental caries, a mildly painful white lesion side effect in the mucosa was noted in a portion of the subjects, which disappeared at 48 hours without treatment. The occurrence of reversible localized changes to the oral mucosa was recognised in the first reports of longitudinal studies.
As such all current manufacturers of silver diammine fluoride for dental use recommend protection of the gingiva (gums) during the topical application of the solution.
Furthermore, the Australian Centre for Population Oral Health (ARCPOH) in Adelaide sought, by way of personal communication with the present Inventor, a water-based version of silver fluoride on account of the ammoniated version of silver fluoride not being received well by the elderly involved in a study into the effect of silver diammine fluoride in preventing root surface caries.
As such, a need therefore exists for a method of stabilising silver fluoride which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.
It is to be understood that, if any prior art information is referred to herein; such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.